International inspectors haven't proved that Iran has a secret nuclear weapons program - but they're getting close.
In one of the most troubling disclosures yet about Tehran's atomic intentions, a new International Atomic Energy Association report says that an IAEA team recently found traces of two types of highly enriched uranium at an Iranian facility.
Iran has denied producing weapons-grade fissile material. Particles of any such uranium must have been on the equipment in question when purchased, said Iranian officials.
But analysts outside the IAEA said such an explanation strains credulity, especially given that Iran delayed inspectors' access to two other uranium sites. At the least, they say, Tehran has a lot of explaining to do. "Iran needs to provide a lot more information very quickly," says David Albright, an expert on nuclear proliferation at the Institute for Science and International Security.
Disclosure of the new IAEA findings comes at a sensitive time for the international community. The next meeting of the IAEA's board of governors is scheduled for Sept. 8, and many expect that the US will push for the board to find Iran in violation of the Non-Proliferation Treaty.
The IAEA would then refer the matter to the UN Security Council, which could vote for economic sanctions against Iran.
"In terms of next steps, the US has been putting pressure on the IAEA," says Paul Kerr, a research analyst at the Arms Control Association.
To this point the US has been content to let the IAEA take the lead in the world's efforts to investigate Iran's suspected nuclear-weapons program.
In some ways US officials see the situation as a test not just of Iran but of the rest of the world's intentions. Russia, Japan, Germany, France, and other nations have long complained about the US predilection for unilateral action in global affairs. Now they're being presented, step by step, with evidence that Iran is cheating on its international agreements.
Thus the US attitude about the IAEA's and UN's role is, to an extent, to ask "what are you all going to do about this?"
"It's a really big test because if these institutions don't prevent Iran from going nuclear, what do they have to complain about the US taking actions on its own?" says Brenda Shaffer, an expert on Iran and Central Asia at Harvard's John F. Kennedy School of Government.
The fact that IAEA inspectors found evidence of possible clandestine work at the Natanz uranium enrichment plant is a good indication that Tehran is further down the road toward obtaining nuclear weapons than many analysts and intelligence agencies had predicted.
Environmental samples taken by the IAEA at the facility between March and June 2003 "indicate the possible presence in Iran of high enriched uranium, material that is not on its inventory of declared nuclear material," says the restricted-distribution report, a copy of which was obtained by the Monitor.
Uranium enrichment is a purification process which creates either fuel for civilian reactors or the fissile core of nuclear weapons. Bomb-grade material must be more highly enriched than its civilian counterpart. Iran says that its nuclear infrastructure is intended to support power-generating reactors. Most of the rest of the world suspects that this is just a cover story, and that Iran really has a multitrack effort under way to obtain a nuclear arsenal.
Some analysts found another part of the IAEA report almost as worrisome as its disclosure about finding trace elements of weapons material.
Iran has admitted doing work on enrichment centrifuges at a second site, known as the Kalaye Electric Co., according to Mr. Albright of ISIS.
The existence of this facility was revealed by an Iranian resistance group, and, until recently, Tehran rebuffed IAEA efforts to enter what it first called a watch factory.
Inspectors found fresh paint and other signs of hurried refurbishment upon their visit. Environmental samples taken at Kalaye have yet to be conclusively analyzed, according to the IAEA report.
Given the context of what the IAEA has discovered it's "legitimate to worry that the [Kalaye] refurbishment is to hide past uranium-enrichment activities," says Albright.